Signal-Copiahan. (Hazlehurst, Copiah County, Miss.) 1885-1888, 1887-11-03
1uNNELlNa THE HUDSON.
Details Explaining tho Work Of Excavation
and Pressure Of Air.


Details Explaining tho Work Of Excavation
and Pressure Of Air.
For seven years work has boon pre-
crossing upon tunnel under the Hud-
son river. between tho Hoboken and
Erie ferries, to connect New York and
Jersey City. Want of funds has pre-
vented its completion ut tho contcm-
plated date. but it is constantly in
crcasing its length, and the meeting Of
the sections seventy feet beneath the
surface of the river il sure to be ac-
complished in the not very remote fi-.
ture. Two tunnels are in fact being
constructed side by side. one OF which
has been extended q distance OF
2,1OO feet, the other $50 feet
The daily average Of progress.
made ut heading is 8! feet.
The exterior OF the tunnel con-
sists of Hanged plates of boilc.
iron bolted together so as to
form circular tube about "a feet in
diameter. Within this iron tube is .
lining of brick q feet thick, giving rig
idity and pcrmancncc to the completed
tunnel. The work is advanced at the
heading by adding one by one Hanged
plates to those already bolted in posi-
ton at the forward end. Excavating
the silt that forms the bed of the Hud-
son, placing the plates, building the
brick work, and advancing the interior
tube, called tho "pilot," all 90 on ut.
the same time. The pilot, an iron
tube feet in diameter and 80 feet
long. is kept about Is feet in advance
of the tunnel itself, and serves some.
what the purpose Of IN outwork for
the advance guard for the gang OF.
workmen engaged in digging. boiling
on plates, and hauling out the cxca-
waited dirt. The pilot is advanced by
dctaching plates from its rear end and
placing them in front rs the work adj
vanccs. 1t might be supposed that
the pressure of GO feet of water above
the mouth of the tunnel would cause
mud and water to enter and overwhclm
the workmcn. This would no doubt
occur but for the system of locks en-
ployed to confinc the air in the end OF
the tunnel when work is going on.
Air is forced in, in fact, until Il pressure
of32 pounds to the square inch is gained.
which pressure, experience shows. suf--
fees to balance the pressure of the
rivor. If the pressure falls below this
figure water begins to tricklo through
the silt into the heading; if it is cx--
ceeded the water is driven out, and the
silt losing Conference, begins to crrmble
and fall down into the heading. Not q
little air escapes, in fact from tho
heading, and produces at the surface
of the river, in midstrcam, q peculiar
circular patch of white foam, due to
the raising of multitude of minute
bubbles. The principle Of the pneu-
matte lock is not unlike that of the Or
binary canal lock. Two walls are built
across the tunnel with n suitable space
between. In these walls are largo
air-tight doors opening inward. When
the workmcn 60 to their work in the
morning they first pass within the outer
wall, and thcreupon the iron door is
shut behind them and air is forced in.
until pressure of32 pounds per square
inch is obtained. When that pressure
is reached the iron door of the inner
wall is easily opened and the men pass
within to the heading. The excavated,
material is hauled out by mules on g,
tramway that travcrses the lock. Light
is obtained from 16 candle-power in
candescent electric lamps. and also
from candles, which burn tiercely I'M.
der the increased pressure of the air.
The tunnels are evidently n difficult
and costly undertaking, but in view of
the great advantage for handling traf-
fc they will give the company who,
owns them, it is somewhat surprising
that money was not forthcoming in.
abundance to secure their completion
years ago. Toavoid the ferries ana DO
able to land traffic of all sorts in New
York without delay ought. one would
think, to excite the transportation COM
panics to make the greatest possible eff
forts. Perhaps there arc vested inter-
csts that find profit in the existing inn
perfect arrangements.--Cor. Chicago